It is well known that more than 70% of illnesses affecting the digestive tract are of a functional nature. Today such illnesses are treated predominantly using pharmacological means. Since drugs generally have side effects, particularly when the drugs only address the symptom and not the underlying problem or dysfunction, they must often be administered for only relatively short period of time. Indeed, if the side effects are sufficiently serious, the drug may have to be discontinued before full benefit to the patient is realized; in many cases the underlying illness remains.
The important role played by electrophysiology in controlling gastrointestinal activity has become increasingly apparent in recent years. Thus, the possibility exists of correcting dysfunction by means of electrical stimulation applied at specific frequencies, sites, and modalities and with regard to the self-regulating electromotor physiology of the gastrointestinal organs or tract. It has recently been shown, for example, that changes occur in the motility and electromotor conduct of the gastric tract in eating disorders (e.g., obesity, thinness, bulimia, anorexia). Disturbances in electromotor activity in diabetic gastroparesis, reflux in the upper digestive tract, and numerous other gastroenterological functional pathologies have also been observed.
In the treatment of obesity, electrical stimulation of the stomach delays the stomach transit by continuous disruption of the intrinsic electrical activity during periods of therapy. Such continuous disruption may result in weight loss by decreasing the cross sectional area of the stomach by inducing contractions, lessening the capacity of the stomach during periods of therapy, changing the intrinsic direction and frequency of the peristalsis during periods of therapy, and modulating the parasympathetic nervous system. Also in the treating obesity, electrical stimulation of the small intestine increases the small intestinal transit time by efficient electrical induction of peristalsis thereby reducing the level of absorbed components. In treatment of gastroparesis and other motility disorders, electrical stimulation improves gastric emptying by accelerating the transit time of food moving through the GI tract and/or relieving neurally mediated symptoms associated with gastroparesis. Thus, electrical stimulation increases frequency or amplitude of peristaltic contractions thereby intensifying the rapidity or force used to propel ingested components through the GI tract.
Recently, methods have been successfully employed whereby an electrical stimulation device is implanted on the stomach wall and/or small intestine. For example, U.S. Pat. No. 5,423,872 (Jun. 13, 1995) provided a process for the treatment of obesity and related disorder employing an electrical stimulator or pacemaker attached to the antrum or greater curvature of the stomach. U.S. Pat. No. 6,615,084 (Sep. 2, 2003) provided a process for the treatment of obesity and related disorder employing an electrical stimulator or pacemaker attached to the lesser curvature of the stomach. U.S. Pat. No. 5,690,691 (Nov. 25, 1997) provided a portable or implantable gastric pacemaker including multiple electrodes positionable on the inner or outer surface of an organ in the gastrointestinal tract which are individually programmed to deliver a phased electrical stimulation to pace peristaltic movement of material through the gastrointestinal tract. U.S. Pat. No. 6,606,523 (Aug. 12, 2003) provided an apparatus for stimulating neuromuscular tissue of the gastrointestinal tract and methods for installing the apparatus to the surface of the neuromuscular tissue. More recently, U.S. patent application Ser. No. 10/627,908 (filed Jul. 25, 2003) provides methods whereby an electrical stimulation device is implanted on the small intestines or lower bowel. All of the patents, patent applications, and publications cited in the present specification are incorporated by reference.
Typically, a lead conveys the electrical stimulation from the electrical stimulator to the gastrointestinal tissue. A known method for implanting such a lead into the gastrointestinal tissue is accomplished by inserting, typically through a trocar (rigid tube with airtight valves), a needle with a thread attached at one end and a lead attached at the other. Another approach utilizes a lead with a needle incorporated into one end, wherein the needle is implanted into the tissue and affixed by tines. However, both of the approaches above have the disadvantage that a tissue tunnel with a large diameter is created upon implantation of the device; such large diameter may allow movement of the electrodes. Such movement may be problematic when targeting particular areas of tissue for stimulation. Moreover, fibrosis and/or erosion, which may result for larger diameter tunnels, may cause a decrease in effectiveness of the therapy, a completely ineffective therapy, and/or tissue damage.
Gastrointestinal stimulation often requires high energy stimulation that is distributed over large electrode surface areas to avoid tissue damage. However, leads that are currently being used to convey electrical stimulation from the electrical stimulator to the gastrointestinal tissue are rigid. Rigid electrodes may be problematic because merely increasing the surface area of a rigid electrode increases the size of the electrode thus increasing the possibility of erosion. Also, rigid electrodes may decrease the compliance of the surrounding tissue and induce mechanical stress concentrations that may result in fatigue failures in the lead.
Therefore, it would be desirable to provide an implantable lead device which may be easily positioned and secured into the tissue. It would also be desirable to provide an implantable lead device which creates a smaller diameter in the tissue tunnel than prior devices, thereby lessening the likelihood that the electrodes will be displaced, especially where the tissue is undergoing repeated and/or vigorous movement. Further, it would be desirable to provide an implantable lead -device which utilizes flexible electrodes to facilitate compliance of the surrounding tissue and decrease the likelihood of mechanical stress concentrations that may result in fatigue failures in the lead.